Egyptian judges have condemned a decree granting President Mohamed Morsi sweeping new powers, as angry protesters clashed with police for a second day.

A handful of rock-throwing activists battled riot police in the streets near Tahrir Square, where several thousand protesters massed on Friday to demonstrate against the decree, which effectively prevents Mr Morsi's decisions from being challenged.

The move also removed powers from the judiciary and allows the president to take any measures to protect national security.

The Supreme Judicial Council, the country's highest judicial authority, said the decree was an "unprecedented attack" on their independence, the state news agency reported.

Judges in the coastal city of Alexandria said all work at courts and prosecution offices would be suspended until the measures were reversed.

Some protesters are staging a sit-in in Tahrir Square

A number of opposition parties have called for an open-ended sit-in with the aim of "toppling" the decree, which has also drawn criticism from the US, the UN and the European Union.

A mass protest has also been called for Tuesday.

"We are facing a historic moment in which we either complete our revolution or we abandon it to become prey for a group that has put its narrow party interests above the national interest," the liberal Dustour Party said in a statement.

Mr Morsi's Muslim Brotherhood party also called its supporters out onto the streets of Cairo on Tuesday for a counter-demonstration to show support for the move.

On Friday, the president addressed his supporters at a rally outside the presidential palace, telling them he would press forward and that he was on the path to "freedom and democracy".

He said that the new powers were designed to stop "weevils" from the regime of ousted former president Hosni Mubarak blocking progress.

The decree reflects the concerns in the Muslim Brotherhood-led government that sections of the judiciary remain unreformed following the overthrown of Mubarak.

"It aims to sideline Morsi's enemies in the judiciary and ultimately to impose and head off any legal challenges to the constitution," said Elijah Zarwan, a Fellow with The European Council on Foreign Relations.

"We are in a situation now where both sides are escalating and it's getting harder and harder to see how either side can gracefully climb down."